2 scc's vs 1 combiner box with blocking diodes for South/East panels

[OffGridIdaho]

Not sure what choice to make.

I want to run two 2,000w solar panel arrays. One facing south and one facing east.

My choice are:

Buy a Victron with 2 solar string inputs
Buy 2 victron single input scc's
Buy 1 combiner box with blocking diodes

The combiner box is by far the cheapest option. Is there a reason I dont want the combiner box?

 

[sunshine_eggo]

The combiner box is by far the cheapest option.

Yep.

Is there a reason I dont want the combiner box?

Nope.

I would argue that the blocking diodes are not mandatory. Even your E panels will be able to produce voltage > Vmp in the evening, but they will produce very little current. The presence of light yields volts. The intensity of light yields amps.

As an example, please look at my MPPT behavior this morning:




The vertical line is 1 minute before sunrise. My MPPT was disabled due to low-temp protection for the Lithium battery, and as you can see near full Voc was achieved just prior to sunrise.

As you can see, my Vmp is around 110V, and it was above that value 15 minutes before sunrise.

Blocking diodes will absolutely guarantee one array won't discharge into the other, but unless you're putting blankets over one of arrays, the array with less intense light will always be able to achieve the Vmp of the array with more insolation insuring no backfeeding.

 

[timselectric]

I have personally tested parallel arrays facing different directions. Both with and without blocking diodes. There was no measurable difference. I can only assume that any benefit was offset by the added resistance of the diodes.

 

[HRTKD]

I have a 1000 watt array 2s2p made from 280 watt panels. I have them arranged in an east/west layout. I used MC4 Y connectors to parallel the two 2s sets of panels. It works fine for me, but with your wattage a Y connector probably isn't a good fit. In that case, a combiner box is the least cost and simple solution.

 

[OffGridIdaho]

Ok thanks guys. So Would there be ANY benefit from having 2 SCC's and a combiner box or 1SCC with dual solar input?

The dang solar suppliers are are telling me to buy 2 scc's.

 

[HRTKD]

Two solar charge controllers would be beneficial if you want some redundancy. But if you're buying quality components, I don't think that's necessary.

As long as you find a solar charge controller that has the right Maximum PV Input Voltage for the 3s configuration and you're not leaving unused PV watts on the table, a single solar charge controller is OK. But you may find that it takes two solar charge controllers to make use of all those watts.

The Victron MPPT calculator is a very good resource.

MPPT Calculator - Victron Energy

MPPT Calculator - Victron Energy

www.victronenergy.com

 

[timselectric]

With two separate SCC's , you could possibly get more production at the small peak of the day. Up to you if it's worth the extra cost of equipment and wiring.

 

[TomC4306]

Three strings at 155°, three strings at 205°, into a Watts 24/7 six to one combiner box.
Works great. Small sacrifice of absolute peak power for a broader parabola of charging.

Edit.. to one 80 amp mppt.

 

[sunshine_eggo]

In my grand plan, I envision over-paneling my MPPT 250/100 to include about 900W of E and W facing arrays in parallel with my 6kW S array. I have everything I need to make it happen except... time.

 

[OffGridIdaho]

Ok so Im looking at 1 scc then.

Of these two, which should I get?

The victron 250/100 is about 1,000 dollars
The Victron 450/100 is about 1300.

Run 1 is 105ft
Run 2 is 130ft

 

[timselectric]

It depends on how you want to wire the panels.
Higher voltage is more efficient and cheaper for wiring.

 

[sunshine_eggo]

It depends on how you want to wire the panels.
Higher voltage is more efficient and cheaper for wiring.

Yep. @OffGridIdaho you'll need to run the numbers on the voltage drop for the two arrays based on Vmp and Isc.

 

[OffGridIdaho]

OK I will run the numbers.

Do any resellers ever discount the victron brand or have sales?
It sucks to pay MAP

 

[HRTKD]

OK I will run the numbers.

Do any resellers ever discount the victron brand or have sales?
It sucks to pay MAP

The discounts are often found only when you talk to the reseller directly. They can't advertise discount prices. Give SolarSupplyHouse.com a call. I used them when I bought my Victron Multiplus. BayMarineSupply.com and AlteStore.com are a couple more to check with. I've bought stuff from all three of those vendors.

 

[HRTKD]

I just received an email from SolarSupplyHouse.com with a 10% off coupon code that is good for Victron too. Use "CYBERWEEK" for the code. Free shipping over $99. They had excellent customer service on the phone when I ordered. They were very familiar with the Victron gear I was buying.

 

[OffGridIdaho]

I just received an email from SolarSupplyHouse.com with a 10% off coupon code that is good for Victron too. Use "CYBERWEEK" for the code. Free shipping over $99. They had excellent customer service on the phone when I ordered. They were very familiar with the Victron gear I was buying.

Ok thanks. They have no phone. Shipping says 7 days.
I called a local shop and they gave me 7% and I can drive and pick it up (100 miles rt). Not sure I want to wait a week for 3%. But 10% is a good deal for sure.

Thx!